CMU or poured concrete

f8lyer8s

I am bumping out my (single car) garage 36" to be flush with the rest of my house. We are getting rid of the garage and extending our family room and kitchen. The garage measures about 10' x 21'. the foundation we have now is poured concrete about 6" thick. I have already cut the driveway and dug my hole. (i am still wating for the township to approve my permits) I originally was going to just match what i already have and pour the concrete. the first pour was going to be loose, 10" thick by about 17" wide. followed by the 2nd pour which i would form, which would be about 36" by 6" thick. the foundation that i am adding would be an L shape. So i started to think today about how i would go about forming the 2nd pour. and making it line up with the house and actually securing it so it is stable enough to hold all the concrete and still keeping it all lined up... This brings me to my "solution" why not just lay block... seems cheaper and easier.. however, i have never done it before but have done some landscaping retaining walls and a little brick work.. but i really dont know much about laying block for foundation walls... as far as what size block i need, how to do the corners, and what type of block do i need. Where to rebar? do i fill all the blocks with mortar or concrete? or just some. what do i do at the top when i am ready for my sill plate besides j bolts. and most importantly, how do i tied it into my existing foundation? or do i just lay it next to it and have it independent? Basically take me from after i dig the hole to ready to frame... all halp is greatly appreciated!

pls8xx

Either CMU or poured will work. Most any DIYer can do block but not with the skill of a blocklayer. The problem will be in getting the final course at a perfect grade. With a poured wall you have more to learn, but it is much easier to finish the top at just the right grade. I mark the grade I want on the forms and then drill a small hole I can push a nail through about every 2 ft along the forms. I can then dress the top to the nails before pulling them.

To do the forms, use some type of snap ties. Or if you have trouble getting the hardware to use the ties, you can do the DIY forming I use. See more on this thread:

Attaching retainer wall forms to foundation

jomama45

That's alot of questions in one post, although they're certainly all good questions. I'll touch on a few now:

- Check out Youtube for videos on laying block. As I recall, "Sakcrete" has a good video, as well as others, laying out the basics.

- For your situation, block is going to be much simpler, easier, and faster IMO.

- Make sure your footing is either perfectly aligned to the existing foundation, or simply make the footing a few inches wider. You need at least 4" minimum of excess footing on both sides of the block wall, and if you end up with less, you could have issues, especially if it's beign inspected.

- 8" wide block should be just fine. Typically, we'll lay 4 courses of 8" regulars/"stretchers", 1 course of 8" solid tops (stretchers over pilasters), an one course of 6" solid tops (again, stretchers over pilasters). The 2" difference in width creates a interior floor ledge for the futrure garage floor to bear on. Anchor bolts are set in the pilasters in grouted and rebar re-enforced cells.

- You can dowel into the existing foundation wall with 3/8" or 1/2" rebar every other course. Leave the end block open and treat it as a pilaster so that the rebar are encased in grout.